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h1. Logging guidelines

h2. Framework

h3. SLF4J (Simple Logging Facade for Java)

"Documentation":http://www.slf4j.org/docs.html

h3. Maven

No dependency SHOULD be added to the module POM. The slf4j dependency is already defined in the ecard client root POM.

slf4j needs a backend implementation. For the tests, logback-classic is pulled in by the root POM. For production use, the client artifact must pull in a compile dependency on a backend and configure it appropriately.

h3. Preamble

<pre>

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

private static final Logger logger = LoggerFactory.getLogger(MYCLASS.class);

</pre>

h2. Levels

h3. Exceptions

<pre>

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

private static final Logger logger = LoggerFactory.getLogger(MYCLASS.class);

try{

 ...

} catch (Exception e){

  logger.error(ex.getMessage(), ex);

}

</pre>

Or set a descriptive message:

<pre>

try{

 ...

} catch (Exception e){

  logger.error("Error while reading value X.", ex);

}

</pre>

h3. Messages

Messages including  APDUs, eCard-API messages, PAOS messages.

<pre>

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

private static final Logger logger = LoggerFactory.getLogger(MYCLASS.class);

logger.debug("Message received:\n{}", message);

logger.debug("Message sent:\n{}", message);

</pre>

h3. Events

E.g. GUI events.

<pre>

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

private static final Logger logger = LoggerFactory.getLogger(MYCLASS.class);

logger.debug("Event: {}", event);

</pre>

h2. Notes

h3. Trace statements as the following example shows are omitted, because there is a "slf4j agent":http://www.slf4j.org/extensions.html#javaagent which can automate this task.

<pre>

public void foo(Bar b) {

    logger.trace("Enter function foo: {}", b);

    ...

</pre>